[PATCH 0/2] HID: Add support for Surface Aggregator Module HID transport

[PATCH 0/2] HID: Add support for Surface Aggregator Module HID transport

[Maximilian Luz]

This series adds support for the Surface System Aggregator Module (SSAM)
HID transport subsystem.

The SSAM is an embedded controller, found on 5th- and later generation
Microsoft Surface devices. On some of these devices (specifically
Surface Laptops 1, 2, and 3, as well as Surface Book 3), built-in input
devices are connected via the SSAM. These devices communicate (mostly)
via normal HID reports, so adding support for them is (mostly) just a
matter of implementing an HID transport driver.

SSAM actually has two different HID interfaces: One (legacy) interface
used on Surface Laptops 1 and 2, and a newer interface for the rest. The
newer interface allows for multiple HID devices to be addressed and is
implemented in the first patch. The older interface only allows a single
HID device to be connected and, furthermore, only allows a single output
report, specifically one for the caps lock LED. This is implemented in
the second patch.

See the commit messages of the respective patches for more details.

Regards,
Max

Note: This patch depends on the

    platform/surface: Add Surface Aggregator device registry

series. More specifically patch

    platform/surface: Set up Surface Aggregator device registry

The full series has been merged into the for-next branch of the
platform-drivers-x86 tree [1]. The commit in question can be found at
[2].

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=for-next
[2]: https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?h=for-next&id=fc622b3d36e6d91330fb21506b9ad1e3206a4dde

Maximilian Luz (2):
  HID: Add support for Surface Aggregator Module HID transport
  HID: surface-hid: Add support for legacy keyboard interface

 MAINTAINERS                                |   7 +
 drivers/hid/Kconfig                        |   2 +
 drivers/hid/Makefile                       |   2 +
 drivers/hid/surface-hid/Kconfig            |  42 +++
 drivers/hid/surface-hid/Makefile           |   7 +
 drivers/hid/surface-hid/surface_hid.c      | 253 +++++++++++++++++
 drivers/hid/surface-hid/surface_hid_core.c | 272 +++++++++++++++++++
 drivers/hid/surface-hid/surface_hid_core.h |  77 ++++++
 drivers/hid/surface-hid/surface_kbd.c      | 300 +++++++++++++++++++++
 9 files changed, 962 insertions(+)
 create mode 100644 drivers/hid/surface-hid/Kconfig
 create mode 100644 drivers/hid/surface-hid/Makefile
 create mode 100644 drivers/hid/surface-hid/surface_hid.c
 create mode 100644 drivers/hid/surface-hid/surface_hid_core.c
 create mode 100644 drivers/hid/surface-hid/surface_hid_core.h
 create mode 100644 drivers/hid/surface-hid/surface_kbd.c

-- 
2.30.1

[PATCH 1/2] HID: Add support for Surface Aggregator Module HID transport

[Maximilian Luz]

Add a HID transport driver to support integrated HID devices on newer
Microsoft Surface models (specifically 7th-generation, i.e. Surface
Laptop 3, Surface Book 3, and later).

On those models, the internal keyboard and touchpad (as well as some
other HID devices with currently unknown function) are connected via the
generic HID subsystem (TC=0x15) of the Surface System Aggregator Module
(SSAM). This subsystem provides a generic HID transport layer, support
for which is implemented by this driver.

Co-developed-by: Blaž Hrastnik <blaz@mxxn.io>
Signed-off-by: Blaž Hrastnik <blaz@mxxn.io>
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
---

Note: This patch depends on the

    platform/surface: Add Surface Aggregator device registry

series. More specifically patch

    platform/surface: Set up Surface Aggregator device registry

The full series has been merged into the for-next branch of the
platform-drivers-x86 tree [1]. The commit in question can be found at
[2].

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=for-next
[2]: https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?h=for-next&id=fc622b3d36e6d91330fb21506b9ad1e3206a4dde

---
 MAINTAINERS                                |   7 +
 drivers/hid/Kconfig                        |   2 +
 drivers/hid/Makefile                       |   2 +
 drivers/hid/surface-hid/Kconfig            |  28 +++
 drivers/hid/surface-hid/Makefile           |   6 +
 drivers/hid/surface-hid/surface_hid.c      | 253 +++++++++++++++++++
 drivers/hid/surface-hid/surface_hid_core.c | 272 +++++++++++++++++++++
 drivers/hid/surface-hid/surface_hid_core.h |  77 ++++++
 8 files changed, 647 insertions(+)
 create mode 100644 drivers/hid/surface-hid/Kconfig
 create mode 100644 drivers/hid/surface-hid/Makefile
 create mode 100644 drivers/hid/surface-hid/surface_hid.c
 create mode 100644 drivers/hid/surface-hid/surface_hid_core.c
 create mode 100644 drivers/hid/surface-hid/surface_hid_core.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 240e8a739fd1..bb6a796dc537 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11817,6 +11817,13 @@ S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git
 F:	drivers/platform/surface/
 
+MICROSOFT SURFACE HID TRANSPORT DRIVER
+M:	Maximilian Luz <luzmaximilian@gmail.com>
+L:	linux-input@vger.kernel.org
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+F:	drivers/hid/surface-hid/
+
 MICROSOFT SURFACE HOT-PLUG DRIVER
 M:	Maximilian Luz <luzmaximilian@gmail.com>
 L:	platform-driver-x86@vger.kernel.org
diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 786b71ef7738..26e06097ba08 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -1206,4 +1206,6 @@ source "drivers/hid/intel-ish-hid/Kconfig"
 
 source "drivers/hid/amd-sfh-hid/Kconfig"
 
+source "drivers/hid/surface-hid/Kconfig"
+
 endmenu
diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index c4f6d5c613dc..1044ed238856 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile
@@ -145,3 +145,5 @@ obj-$(CONFIG_INTEL_ISH_HID)	+= intel-ish-hid/
 obj-$(INTEL_ISH_FIRMWARE_DOWNLOADER)	+= intel-ish-hid/
 
 obj-$(CONFIG_AMD_SFH_HID)       += amd-sfh-hid/
+
+obj-$(CONFIG_SURFACE_HID_CORE)  += surface-hid/
diff --git a/drivers/hid/surface-hid/Kconfig b/drivers/hid/surface-hid/Kconfig
new file mode 100644
index 000000000000..642c7f0e64fe
--- /dev/null
+++ b/drivers/hid/surface-hid/Kconfig
@@ -0,0 +1,28 @@
+# SPDX-License-Identifier: GPL-2.0+
+menu "Surface System Aggregator Module HID support"
+	depends on SURFACE_AGGREGATOR
+	depends on INPUT
+
+config SURFACE_HID
+	tristate "HID transport driver for Surface System Aggregator Module"
+	depends on SURFACE_AGGREGATOR_REGISTRY
+	select SURFACE_HID_CORE
+	help
+	  Driver to support integrated HID devices on newer Microsoft Surface
+	  models.
+
+	  This driver provides support for the HID transport protocol provided
+	  by the Surface Aggregator Module (i.e. the embedded controller) on
+	  7th-generation Microsoft Surface devices, i.e. Surface Book 3 and
+	  Surface Laptop 3. On those models, it is mainly used to connect the
+	  integrated touchpad and keyboard.
+
+	  Say M or Y here, if you want support for integrated HID devices, i.e.
+	  integrated touchpad and keyboard, on 7th generation Microsoft Surface
+	  models.
+
+endmenu
+
+config SURFACE_HID_CORE
+	tristate
+	select HID
diff --git a/drivers/hid/surface-hid/Makefile b/drivers/hid/surface-hid/Makefile
new file mode 100644
index 000000000000..62fc04632d3d
--- /dev/null
+++ b/drivers/hid/surface-hid/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Makefile - Surface System Aggregator Module (SSAM) HID transport driver.
+#
+obj-$(CONFIG_SURFACE_HID_CORE)	+= surface_hid_core.o
+obj-$(CONFIG_SURFACE_HID)	+= surface_hid.o
diff --git a/drivers/hid/surface-hid/surface_hid.c b/drivers/hid/surface-hid/surface_hid.c
new file mode 100644
index 000000000000..3477b31611ae
--- /dev/null
+++ b/drivers/hid/surface-hid/surface_hid.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Surface System Aggregator Module (SSAM) HID transport driver for the
+ * generic HID interface (HID/TC=0x15 subsystem). Provides support for
+ * integrated HID devices on Surface Laptop 3, Book 3, and later.
+ *
+ * Copyright (C) 2019-2021 Blaž Hrastnik <blaz@mxxn.io>,
+ *                         Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#include <asm/unaligned.h>
+#include <linux/hid.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include <linux/surface_aggregator/controller.h>
+#include <linux/surface_aggregator/device.h>
+
+#include "surface_hid_core.h"
+
+
+/* -- SAM interface. -------------------------------------------------------- */
+
+struct surface_hid_buffer_slice {
+	__u8 entry;
+	__le32 offset;
+	__le32 length;
+	__u8 end;
+	__u8 data[];
+} __packed;
+
+static_assert(sizeof(struct surface_hid_buffer_slice) == 10);
+
+enum surface_hid_cid {
+	SURFACE_HID_CID_OUTPUT_REPORT      = 0x01,
+	SURFACE_HID_CID_GET_FEATURE_REPORT = 0x02,
+	SURFACE_HID_CID_SET_FEATURE_REPORT = 0x03,
+	SURFACE_HID_CID_GET_DESCRIPTOR     = 0x04,
+};
+
+static int ssam_hid_get_descriptor(struct surface_hid_device *shid, u8 entry, u8 *buf, size_t len)
+{
+	u8 buffer[sizeof(struct surface_hid_buffer_slice) + 0x76];
+	struct surface_hid_buffer_slice *slice;
+	struct ssam_request rqst;
+	struct ssam_response rsp;
+	u32 buffer_len, offset, length;
+	int status;
+
+	/*
+	 * Note: The 0x76 above has been chosen because that's what's used by
+	 * the Windows driver. Together with the header, this leads to a 128
+	 * byte payload in total.
+	 */
+
+	buffer_len = ARRAY_SIZE(buffer) - sizeof(struct surface_hid_buffer_slice);
+
+	rqst.target_category = shid->uid.category;
+	rqst.target_id = shid->uid.target;
+	rqst.command_id = SURFACE_HID_CID_GET_DESCRIPTOR;
+	rqst.instance_id = shid->uid.instance;
+	rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
+	rqst.length = sizeof(struct surface_hid_buffer_slice);
+	rqst.payload = buffer;
+
+	rsp.capacity = ARRAY_SIZE(buffer);
+	rsp.pointer = buffer;
+
+	slice = (struct surface_hid_buffer_slice *)buffer;
+	slice->entry = entry;
+	slice->end = 0;
+
+	offset = 0;
+	length = buffer_len;
+
+	while (!slice->end && offset < len) {
+		put_unaligned_le32(offset, &slice->offset);
+		put_unaligned_le32(length, &slice->length);
+
+		rsp.length = 0;
+
+		status = ssam_retry(ssam_request_sync_onstack, shid->ctrl, &rqst, &rsp,
+				    sizeof(*slice));
+		if (status)
+			return status;
+
+		offset = get_unaligned_le32(&slice->offset);
+		length = get_unaligned_le32(&slice->length);
+
+		/* Don't mess stuff up in case we receive garbage. */
+		if (length > buffer_len || offset > len)
+			return -EPROTO;
+
+		if (offset + length > len)
+			length = len - offset;
+
+		memcpy(buf + offset, &slice->data[0], length);
+
+		offset += length;
+		length = buffer_len;
+	}
+
+	if (offset != len) {
+		dev_err(shid->dev, "unexpected descriptor length: got %u, expected %zu\n",
+			offset, len);
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+static int ssam_hid_set_raw_report(struct surface_hid_device *shid, u8 rprt_id, bool feature,
+				   u8 *buf, size_t len)
+{
+	struct ssam_request rqst;
+	u8 cid;
+
+	if (feature)
+		cid = SURFACE_HID_CID_SET_FEATURE_REPORT;
+	else
+		cid = SURFACE_HID_CID_OUTPUT_REPORT;
+
+	rqst.target_category = shid->uid.category;
+	rqst.target_id = shid->uid.target;
+	rqst.instance_id = shid->uid.instance;
+	rqst.command_id = cid;
+	rqst.flags = 0;
+	rqst.length = len;
+	rqst.payload = buf;
+
+	buf[0] = rprt_id;
+
+	return ssam_retry(ssam_request_sync, shid->ctrl, &rqst, NULL);
+}
+
+static int ssam_hid_get_raw_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	struct ssam_request rqst;
+	struct ssam_response rsp;
+
+	rqst.target_category = shid->uid.category;
+	rqst.target_id = shid->uid.target;
+	rqst.instance_id = shid->uid.instance;
+	rqst.command_id = SURFACE_HID_CID_GET_FEATURE_REPORT;
+	rqst.flags = 0;
+	rqst.length = sizeof(rprt_id);
+	rqst.payload = &rprt_id;
+
+	rsp.capacity = len;
+	rsp.length = 0;
+	rsp.pointer = buf;
+
+	return ssam_retry(ssam_request_sync_onstack, shid->ctrl, &rqst, &rsp, sizeof(rprt_id));
+}
+
+static u32 ssam_hid_event_fn(struct ssam_event_notifier *nf, const struct ssam_event *event)
+{
+	struct surface_hid_device *shid = container_of(nf, struct surface_hid_device, notif);
+
+	if (event->command_id != 0x00)
+		return 0;
+
+	hid_input_report(shid->hid, HID_INPUT_REPORT, (u8 *)&event->data[0], event->length, 0);
+	return SSAM_NOTIF_HANDLED;
+}
+
+
+/* -- Transport driver. ----------------------------------------------------- */
+
+static int shid_output_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	int status;
+
+	status = ssam_hid_set_raw_report(shid, rprt_id, false, buf, len);
+	return status >= 0 ? len : status;
+}
+
+static int shid_get_feature_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	int status;
+
+	status = ssam_hid_get_raw_report(shid, rprt_id, buf, len);
+	return status >= 0 ? len : status;
+}
+
+static int shid_set_feature_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	int status;
+
+	status = ssam_hid_set_raw_report(shid, rprt_id, true, buf, len);
+	return status >= 0 ? len : status;
+}
+
+
+/* -- Driver setup. --------------------------------------------------------- */
+
+static int surface_hid_probe(struct ssam_device *sdev)
+{
+	struct surface_hid_device *shid;
+
+	shid = devm_kzalloc(&sdev->dev, sizeof(*shid), GFP_KERNEL);
+	if (!shid)
+		return -ENOMEM;
+
+	shid->dev = &sdev->dev;
+	shid->ctrl = sdev->ctrl;
+	shid->uid = sdev->uid;
+
+	shid->notif.base.priority = 1;
+	shid->notif.base.fn = ssam_hid_event_fn;
+	shid->notif.event.reg = SSAM_EVENT_REGISTRY_REG;
+	shid->notif.event.id.target_category = sdev->uid.category;
+	shid->notif.event.id.instance = sdev->uid.instance;
+	shid->notif.event.mask = SSAM_EVENT_MASK_STRICT;
+	shid->notif.event.flags = 0;
+
+	shid->ops.get_descriptor = ssam_hid_get_descriptor;
+	shid->ops.output_report = shid_output_report;
+	shid->ops.get_feature_report = shid_get_feature_report;
+	shid->ops.set_feature_report = shid_set_feature_report;
+
+	ssam_device_set_drvdata(sdev, shid);
+	return surface_hid_device_add(shid);
+}
+
+static void surface_hid_remove(struct ssam_device *sdev)
+{
+	surface_hid_device_destroy(ssam_device_get_drvdata(sdev));
+}
+
+static const struct ssam_device_id surface_hid_match[] = {
+	{ SSAM_SDEV(HID, 0x02, SSAM_ANY_IID, 0x00) },
+	{ },
+};
+MODULE_DEVICE_TABLE(ssam, surface_hid_match);
+
+static struct ssam_device_driver surface_hid_driver = {
+	.probe = surface_hid_probe,
+	.remove = surface_hid_remove,
+	.match_table = surface_hid_match,
+	.driver = {
+		.name = "surface_hid",
+		.pm = &surface_hid_pm_ops,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+module_ssam_device_driver(surface_hid_driver);
+
+MODULE_AUTHOR("Blaž Hrastnik <blaz@mxxn.io>");
+MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
+MODULE_DESCRIPTION("HID transport driver for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");
diff --git a/drivers/hid/surface-hid/surface_hid_core.c b/drivers/hid/surface-hid/surface_hid_core.c
new file mode 100644
index 000000000000..7b27ec392232
--- /dev/null
+++ b/drivers/hid/surface-hid/surface_hid_core.c
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Common/core components for the Surface System Aggregator Module (SSAM) HID
+ * transport driver. Provides support for integrated HID devices on Microsoft
+ * Surface models.
+ *
+ * Copyright (C) 2019-2021 Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#include <asm/unaligned.h>
+#include <linux/hid.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/usb/ch9.h>
+
+#include <linux/surface_aggregator/controller.h>
+
+#include "surface_hid_core.h"
+
+
+/* -- Device descriptor access. --------------------------------------------- */
+
+static int surface_hid_load_hid_descriptor(struct surface_hid_device *shid)
+{
+	int status;
+
+	status = shid->ops.get_descriptor(shid, SURFACE_HID_DESC_HID,
+			(u8 *)&shid->hid_desc, sizeof(shid->hid_desc));
+	if (status)
+		return status;
+
+	if (shid->hid_desc.desc_len != sizeof(shid->hid_desc)) {
+		dev_err(shid->dev, "unexpected HID descriptor length: got %u, expected %zu\n",
+			shid->hid_desc.desc_len, sizeof(shid->hid_desc));
+		return -EPROTO;
+	}
+
+	if (shid->hid_desc.desc_type != HID_DT_HID) {
+		dev_err(shid->dev, "unexpected HID descriptor type: got %#04x, expected %#04x\n",
+			shid->hid_desc.desc_type, HID_DT_HID);
+		return -EPROTO;
+	}
+
+	if (shid->hid_desc.num_descriptors != 1) {
+		dev_err(shid->dev, "unexpected number of descriptors: got %u, expected 1\n",
+			shid->hid_desc.num_descriptors);
+		return -EPROTO;
+	}
+
+	if (shid->hid_desc.report_desc_type != HID_DT_REPORT) {
+		dev_err(shid->dev, "unexpected report descriptor type: got %#04x, expected %#04x\n",
+			shid->hid_desc.report_desc_type, HID_DT_REPORT);
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+static int surface_hid_load_device_attributes(struct surface_hid_device *shid)
+{
+	int status;
+
+	status = shid->ops.get_descriptor(shid, SURFACE_HID_DESC_ATTRS,
+			(u8 *)&shid->attrs, sizeof(shid->attrs));
+	if (status)
+		return status;
+
+	if (get_unaligned_le32(&shid->attrs.length) != sizeof(shid->attrs)) {
+		dev_err(shid->dev, "unexpected attribute length: got %u, expected %zu\n",
+			get_unaligned_le32(&shid->attrs.length), sizeof(shid->attrs));
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+
+/* -- Transport driver (common). -------------------------------------------- */
+
+static int surface_hid_start(struct hid_device *hid)
+{
+	struct surface_hid_device *shid = hid->driver_data;
+
+	return ssam_notifier_register(shid->ctrl, &shid->notif);
+}
+
+static void surface_hid_stop(struct hid_device *hid)
+{
+	struct surface_hid_device *shid = hid->driver_data;
+
+	/* Note: This call will log errors for us, so ignore them here. */
+	ssam_notifier_unregister(shid->ctrl, &shid->notif);
+}
+
+static int surface_hid_open(struct hid_device *hid)
+{
+	return 0;
+}
+
+static void surface_hid_close(struct hid_device *hid)
+{
+}
+
+static int surface_hid_parse(struct hid_device *hid)
+{
+	struct surface_hid_device *shid = hid->driver_data;
+	size_t len = get_unaligned_le16(&shid->hid_desc.report_desc_len);
+	u8 *buf;
+	int status;
+
+	buf = kzalloc(len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	status = shid->ops.get_descriptor(shid, SURFACE_HID_DESC_REPORT, buf, len);
+	if (!status)
+		status = hid_parse_report(hid, buf, len);
+
+	kfree(buf);
+	return status;
+}
+
+static int surface_hid_raw_request(struct hid_device *hid, unsigned char reportnum, u8 *buf,
+				   size_t len, unsigned char rtype, int reqtype)
+{
+	struct surface_hid_device *shid = hid->driver_data;
+
+	if (rtype == HID_OUTPUT_REPORT && reqtype == HID_REQ_SET_REPORT)
+		return shid->ops.output_report(shid, reportnum, buf, len);
+
+	else if (rtype == HID_FEATURE_REPORT && reqtype == HID_REQ_GET_REPORT)
+		return shid->ops.get_feature_report(shid, reportnum, buf, len);
+
+	else if (rtype == HID_FEATURE_REPORT && reqtype == HID_REQ_SET_REPORT)
+		return shid->ops.set_feature_report(shid, reportnum, buf, len);
+
+	return -EIO;
+}
+
+static struct hid_ll_driver surface_hid_ll_driver = {
+	.start       = surface_hid_start,
+	.stop        = surface_hid_stop,
+	.open        = surface_hid_open,
+	.close       = surface_hid_close,
+	.parse       = surface_hid_parse,
+	.raw_request = surface_hid_raw_request,
+};
+
+
+/* -- Common device setup. -------------------------------------------------- */
+
+int surface_hid_device_add(struct surface_hid_device *shid)
+{
+	int status;
+
+	status = surface_hid_load_hid_descriptor(shid);
+	if (status)
+		return status;
+
+	status = surface_hid_load_device_attributes(shid);
+	if (status)
+		return status;
+
+	shid->hid = hid_allocate_device();
+	if (IS_ERR(shid->hid))
+		return PTR_ERR(shid->hid);
+
+	shid->hid->dev.parent = shid->dev;
+	shid->hid->bus = BUS_HOST;
+	shid->hid->vendor = cpu_to_le16(shid->attrs.vendor);
+	shid->hid->product = cpu_to_le16(shid->attrs.product);
+	shid->hid->version = cpu_to_le16(shid->hid_desc.hid_version);
+	shid->hid->country = shid->hid_desc.country_code;
+
+	snprintf(shid->hid->name, sizeof(shid->hid->name), "Microsoft Surface %04X:%04X",
+		 shid->hid->vendor, shid->hid->product);
+
+	strscpy(shid->hid->phys, dev_name(shid->dev), sizeof(shid->hid->phys));
+
+	shid->hid->driver_data = shid;
+	shid->hid->ll_driver = &surface_hid_ll_driver;
+
+	status = hid_add_device(shid->hid);
+	if (status)
+		hid_destroy_device(shid->hid);
+
+	return status;
+}
+EXPORT_SYMBOL_GPL(surface_hid_device_add);
+
+void surface_hid_device_destroy(struct surface_hid_device *shid)
+{
+	hid_destroy_device(shid->hid);
+}
+EXPORT_SYMBOL_GPL(surface_hid_device_destroy);
+
+
+/* -- PM ops. --------------------------------------------------------------- */
+
+#ifdef CONFIG_PM_SLEEP
+
+static int surface_hid_suspend(struct device *dev)
+{
+	struct surface_hid_device *d = dev_get_drvdata(dev);
+
+	if (d->hid->driver && d->hid->driver->suspend)
+		return d->hid->driver->suspend(d->hid, PMSG_SUSPEND);
+
+	return 0;
+}
+
+static int surface_hid_resume(struct device *dev)
+{
+	struct surface_hid_device *d = dev_get_drvdata(dev);
+
+	if (d->hid->driver && d->hid->driver->resume)
+		return d->hid->driver->resume(d->hid);
+
+	return 0;
+}
+
+static int surface_hid_freeze(struct device *dev)
+{
+	struct surface_hid_device *d = dev_get_drvdata(dev);
+
+	if (d->hid->driver && d->hid->driver->suspend)
+		return d->hid->driver->suspend(d->hid, PMSG_FREEZE);
+
+	return 0;
+}
+
+static int surface_hid_poweroff(struct device *dev)
+{
+	struct surface_hid_device *d = dev_get_drvdata(dev);
+
+	if (d->hid->driver && d->hid->driver->suspend)
+		return d->hid->driver->suspend(d->hid, PMSG_HIBERNATE);
+
+	return 0;
+}
+
+static int surface_hid_restore(struct device *dev)
+{
+	struct surface_hid_device *d = dev_get_drvdata(dev);
+
+	if (d->hid->driver && d->hid->driver->reset_resume)
+		return d->hid->driver->reset_resume(d->hid);
+
+	return 0;
+}
+
+const struct dev_pm_ops surface_hid_pm_ops = {
+	.freeze   = surface_hid_freeze,
+	.thaw     = surface_hid_resume,
+	.suspend  = surface_hid_suspend,
+	.resume   = surface_hid_resume,
+	.poweroff = surface_hid_poweroff,
+	.restore  = surface_hid_restore,
+};
+EXPORT_SYMBOL_GPL(surface_hid_pm_ops);
+
+#else /* CONFIG_PM_SLEEP */
+
+const struct dev_pm_ops surface_hid_pm_ops = { };
+EXPORT_SYMBOL_GPL(surface_hid_pm_ops);
+
+#endif /* CONFIG_PM_SLEEP */
+
+MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
+MODULE_DESCRIPTION("HID transport driver core for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");
diff --git a/drivers/hid/surface-hid/surface_hid_core.h b/drivers/hid/surface-hid/surface_hid_core.h
new file mode 100644
index 000000000000..4b1a7b57e035
--- /dev/null
+++ b/drivers/hid/surface-hid/surface_hid_core.h
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Common/core components for the Surface System Aggregator Module (SSAM) HID
+ * transport driver. Provides support for integrated HID devices on Microsoft
+ * Surface models.
+ *
+ * Copyright (C) 2019-2021 Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#ifndef SURFACE_HID_CORE_H
+#define SURFACE_HID_CORE_H
+
+#include <linux/hid.h>
+#include <linux/pm.h>
+#include <linux/types.h>
+
+#include <linux/surface_aggregator/controller.h>
+#include <linux/surface_aggregator/device.h>
+
+enum surface_hid_descriptor_entry {
+	SURFACE_HID_DESC_HID    = 0,
+	SURFACE_HID_DESC_REPORT = 1,
+	SURFACE_HID_DESC_ATTRS  = 2,
+};
+
+struct surface_hid_descriptor {
+	__u8 desc_len;			/* = 9 */
+	__u8 desc_type;			/* = HID_DT_HID */
+	__le16 hid_version;
+	__u8 country_code;
+	__u8 num_descriptors;		/* = 1 */
+
+	__u8 report_desc_type;		/* = HID_DT_REPORT */
+	__le16 report_desc_len;
+} __packed;
+
+static_assert(sizeof(struct surface_hid_descriptor) == 9);
+
+struct surface_hid_attributes {
+	__le32 length;
+	__le16 vendor;
+	__le16 product;
+	__le16 version;
+	__u8 _unknown[22];
+} __packed;
+
+static_assert(sizeof(struct surface_hid_attributes) == 32);
+
+struct surface_hid_device;
+
+struct surface_hid_device_ops {
+	int (*get_descriptor)(struct surface_hid_device *shid, u8 entry, u8 *buf, size_t len);
+	int (*output_report)(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len);
+	int (*get_feature_report)(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len);
+	int (*set_feature_report)(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len);
+};
+
+struct surface_hid_device {
+	struct device *dev;
+	struct ssam_controller *ctrl;
+	struct ssam_device_uid uid;
+
+	struct surface_hid_descriptor hid_desc;
+	struct surface_hid_attributes attrs;
+
+	struct ssam_event_notifier notif;
+	struct hid_device *hid;
+
+	struct surface_hid_device_ops ops;
+};
+
+int surface_hid_device_add(struct surface_hid_device *shid);
+void surface_hid_device_destroy(struct surface_hid_device *shid);
+
+extern const struct dev_pm_ops surface_hid_pm_ops;
+
+#endif /* SURFACE_HID_CORE_H */
-- 
2.30.1

[PATCH 2/2] HID: surface-hid: Add support for legacy keyboard interface

[Maximilian Luz]

Add support for the legacy keyboard (KBD/TC=0x08) HID transport layer of
the Surface System Aggregator Module (SSAM) to the Surface HID driver.
On Surface Laptops 1 and 2, this interface is used to connect the
integrated keyboard.

Note that this subsystem interface essentially provides a limited HID
transport layer. In contrast to the generic HID interface (TC=0x15) used
on newer Surface models, this interface only allows (as far as we know)
for a single device to be connected and is otherwise severely limited in
terms of support for feature- and output-reports. Specifically, only
caps-lock-LED output-reports and a single read-only feature-report are
supported.

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
---

Note: This patch depends on the

    platform/surface: Add Surface Aggregator device registry

series. More specifically patch

    platform/surface: Set up Surface Aggregator device registry

The full series has been merged into the for-next branch of the
platform-drivers-x86 tree [1]. The commit in question can be found at
[2].

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=for-next
[2]: https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?h=for-next&id=fc622b3d36e6d91330fb21506b9ad1e3206a4dde

---
 drivers/hid/surface-hid/Kconfig       |  14 ++
 drivers/hid/surface-hid/Makefile      |   1 +
 drivers/hid/surface-hid/surface_kbd.c | 300 ++++++++++++++++++++++++++
 3 files changed, 315 insertions(+)
 create mode 100644 drivers/hid/surface-hid/surface_kbd.c

diff --git a/drivers/hid/surface-hid/Kconfig b/drivers/hid/surface-hid/Kconfig
index 642c7f0e64fe..7ce9b5d641eb 100644
--- a/drivers/hid/surface-hid/Kconfig
+++ b/drivers/hid/surface-hid/Kconfig
@@ -21,6 +21,20 @@ config SURFACE_HID
 	  integrated touchpad and keyboard, on 7th generation Microsoft Surface
 	  models.
 
+config SURFACE_KBD
+	tristate "HID keyboard transport driver for Surface System Aggregator Module"
+	select SURFACE_HID_CORE
+	help
+	  Driver to support HID keyboards on Surface Laptop 1 and 2 devices.
+
+	  This driver provides support for the HID transport protocol provided
+	  by the Surface Aggregator Module (i.e. the embedded controller) on
+	  Microsoft Surface Laptops 1 and 2. It is used to connect the
+	  integrated keyboard on those devices.
+
+	  Say M or Y here, if you want support for the integrated keyboard on
+	  Microsoft Surface Laptops 1 and 2.
+
 endmenu
 
 config SURFACE_HID_CORE
diff --git a/drivers/hid/surface-hid/Makefile b/drivers/hid/surface-hid/Makefile
index 62fc04632d3d..4ae11cf09b25 100644
--- a/drivers/hid/surface-hid/Makefile
+++ b/drivers/hid/surface-hid/Makefile
@@ -4,3 +4,4 @@
 #
 obj-$(CONFIG_SURFACE_HID_CORE)	+= surface_hid_core.o
 obj-$(CONFIG_SURFACE_HID)	+= surface_hid.o
+obj-$(CONFIG_SURFACE_KBD)	+= surface_kbd.o
diff --git a/drivers/hid/surface-hid/surface_kbd.c b/drivers/hid/surface-hid/surface_kbd.c
new file mode 100644
index 000000000000..0635341bc517
--- /dev/null
+++ b/drivers/hid/surface-hid/surface_kbd.c
@@ -0,0 +1,300 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Surface System Aggregator Module (SSAM) HID transport driver for the legacy
+ * keyboard interface (KBD/TC=0x08 subsystem). Provides support for the
+ * integrated HID keyboard on Surface Laptops 1 and 2.
+ *
+ * Copyright (C) 2019-2021 Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#include <asm/unaligned.h>
+#include <linux/hid.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+
+#include <linux/surface_aggregator/controller.h>
+
+#include "surface_hid_core.h"
+
+
+/* -- SAM interface (KBD). -------------------------------------------------- */
+
+#define KBD_FEATURE_REPORT_SIZE			7  /* 6 + report ID */
+
+enum surface_kbd_cid {
+	SURFACE_KBD_CID_GET_DESCRIPTOR		= 0x00,
+	SURFACE_KBD_CID_SET_CAPSLOCK_LED	= 0x01,
+	SURFACE_KBD_CID_EVT_INPUT_GENERIC	= 0x03,
+	SURFACE_KBD_CID_EVT_INPUT_HOTKEYS	= 0x04,
+	SURFACE_KBD_CID_GET_FEATURE_REPORT	= 0x0b,
+};
+
+static int ssam_kbd_get_descriptor(struct surface_hid_device *shid, u8 entry, u8 *buf, size_t len)
+{
+	struct ssam_request rqst;
+	struct ssam_response rsp;
+	int status;
+
+	rqst.target_category = shid->uid.category;
+	rqst.target_id = shid->uid.target;
+	rqst.command_id = SURFACE_KBD_CID_GET_DESCRIPTOR;
+	rqst.instance_id = shid->uid.instance;
+	rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
+	rqst.length = sizeof(entry);
+	rqst.payload = &entry;
+
+	rsp.capacity = len;
+	rsp.length = 0;
+	rsp.pointer = buf;
+
+	status = ssam_retry(ssam_request_sync_onstack, shid->ctrl, &rqst, &rsp, sizeof(entry));
+	if (status)
+		return status;
+
+	if (rsp.length != len) {
+		dev_err(shid->dev, "invalid descriptor length: got %zu, expected, %zu\n",
+			rsp.length, len);
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+static int ssam_kbd_set_caps_led(struct surface_hid_device *shid, bool value)
+{
+	struct ssam_request rqst;
+	u8 value_u8 = value;
+
+	rqst.target_category = shid->uid.category;
+	rqst.target_id = shid->uid.target;
+	rqst.command_id = SURFACE_KBD_CID_SET_CAPSLOCK_LED;
+	rqst.instance_id = shid->uid.instance;
+	rqst.flags = 0;
+	rqst.length = sizeof(value_u8);
+	rqst.payload = &value_u8;
+
+	return ssam_retry(ssam_request_sync_onstack, shid->ctrl, &rqst, NULL, sizeof(value_u8));
+}
+
+static int ssam_kbd_get_feature_report(struct surface_hid_device *shid, u8 *buf, size_t len)
+{
+	struct ssam_request rqst;
+	struct ssam_response rsp;
+	u8 payload = 0;
+	int status;
+
+	rqst.target_category = shid->uid.category;
+	rqst.target_id = shid->uid.target;
+	rqst.command_id = SURFACE_KBD_CID_GET_FEATURE_REPORT;
+	rqst.instance_id = shid->uid.instance;
+	rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
+	rqst.length = sizeof(payload);
+	rqst.payload = &payload;
+
+	rsp.capacity = len;
+	rsp.length = 0;
+	rsp.pointer = buf;
+
+	status = ssam_retry(ssam_request_sync_onstack, shid->ctrl, &rqst, &rsp, sizeof(payload));
+	if (status)
+		return status;
+
+	if (rsp.length != len) {
+		dev_err(shid->dev, "invalid feature report length: got %zu, expected, %zu\n",
+			rsp.length, len);
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+static bool ssam_kbd_is_input_event(const struct ssam_event *event)
+{
+	if (event->command_id == SURFACE_KBD_CID_EVT_INPUT_GENERIC)
+		return true;
+
+	if (event->command_id == SURFACE_KBD_CID_EVT_INPUT_HOTKEYS)
+		return true;
+
+	return false;
+}
+
+static u32 ssam_kbd_event_fn(struct ssam_event_notifier *nf, const struct ssam_event *event)
+{
+	struct surface_hid_device *shid = container_of(nf, struct surface_hid_device, notif);
+
+	/*
+	 * Check against device UID manually, as registry and device target
+	 * category doesn't line up.
+	 */
+
+	if (shid->uid.category != event->target_category)
+		return 0;
+
+	if (shid->uid.target != event->target_id)
+		return 0;
+
+	if (shid->uid.instance != event->instance_id)
+		return 0;
+
+	if (!ssam_kbd_is_input_event(event))
+		return 0;
+
+	hid_input_report(shid->hid, HID_INPUT_REPORT, (u8 *)&event->data[0], event->length, 0);
+	return SSAM_NOTIF_HANDLED;
+}
+
+
+/* -- Transport driver (KBD). ----------------------------------------------- */
+
+static int skbd_get_caps_led_value(struct hid_device *hid, u8 rprt_id, u8 *buf, size_t len)
+{
+	struct hid_field *field;
+	unsigned int offset, size;
+	int i;
+
+	/* Get LED field. */
+	field = hidinput_get_led_field(hid);
+	if (!field)
+		return -ENOENT;
+
+	/* Check if we got the correct report. */
+	if (len != hid_report_len(field->report))
+		return -ENOENT;
+
+	if (rprt_id != field->report->id)
+		return -ENOENT;
+
+	/* Get caps lock LED index. */
+	for (i = 0; i < field->report_count; i++)
+		if ((field->usage[i].hid & 0xffff) == 0x02)
+			break;
+
+	if (i == field->report_count)
+		return -ENOENT;
+
+	/* Extract value. */
+	size = field->report_size;
+	offset = field->report_offset + i * size;
+	return !!hid_field_extract(hid, buf + 1, size, offset);
+}
+
+static int skbd_output_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	int caps_led;
+	int status;
+
+	caps_led = skbd_get_caps_led_value(shid->hid, rprt_id, buf, len);
+	if (caps_led < 0)
+		return -EIO;  /* Only caps LED output reports are supported. */
+
+	status = ssam_kbd_set_caps_led(shid, caps_led);
+	if (status < 0)
+		return status;
+
+	return len;
+}
+
+static int skbd_get_feature_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	u8 report[KBD_FEATURE_REPORT_SIZE];
+	int status;
+
+	/*
+	 * The keyboard only has a single hard-coded read-only feature report
+	 * of size KBD_FEATURE_REPORT_SIZE. Try to load it and compare its
+	 * report ID against the requested one.
+	 */
+
+	if (len < ARRAY_SIZE(report))
+		return -ENOSPC;
+
+	status = ssam_kbd_get_feature_report(shid, report, ARRAY_SIZE(report));
+	if (status < 0)
+		return status;
+
+	if (rprt_id != report[0])
+		return -ENOENT;
+
+	memcpy(buf, report, ARRAY_SIZE(report));
+	return len;
+}
+
+static int skbd_set_feature_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	/* Not supported. See skbd_get_feature_report() for details. */
+	return -EIO;
+}
+
+
+/* -- Driver setup. --------------------------------------------------------- */
+
+static int surface_kbd_probe(struct platform_device *pdev)
+{
+	struct ssam_controller *ctrl;
+	struct surface_hid_device *shid;
+
+	/* Add device link to EC. */
+	ctrl = ssam_client_bind(&pdev->dev);
+	if (IS_ERR(ctrl))
+		return PTR_ERR(ctrl) == -ENODEV ? -EPROBE_DEFER : PTR_ERR(ctrl);
+
+	shid = devm_kzalloc(&pdev->dev, sizeof(*shid), GFP_KERNEL);
+	if (!shid)
+		return -ENOMEM;
+
+	shid->dev = &pdev->dev;
+	shid->ctrl = ctrl;
+
+	shid->uid.domain = SSAM_DOMAIN_SERIALHUB;
+	shid->uid.category = SSAM_SSH_TC_KBD;
+	shid->uid.target = 2;
+	shid->uid.instance = 0;
+	shid->uid.function = 0;
+
+	shid->notif.base.priority = 1;
+	shid->notif.base.fn = ssam_kbd_event_fn;
+	shid->notif.event.reg = SSAM_EVENT_REGISTRY_SAM;
+	shid->notif.event.id.target_category = shid->uid.category;
+	shid->notif.event.id.instance = shid->uid.instance;
+	shid->notif.event.mask = SSAM_EVENT_MASK_NONE;
+	shid->notif.event.flags = 0;
+
+	shid->ops.get_descriptor = ssam_kbd_get_descriptor;
+	shid->ops.output_report = skbd_output_report;
+	shid->ops.get_feature_report = skbd_get_feature_report;
+	shid->ops.set_feature_report = skbd_set_feature_report;
+
+	platform_set_drvdata(pdev, shid);
+	return surface_hid_device_add(shid);
+}
+
+static int surface_kbd_remove(struct platform_device *pdev)
+{
+	surface_hid_device_destroy(platform_get_drvdata(pdev));
+	return 0;
+}
+
+static const struct acpi_device_id surface_kbd_match[] = {
+	{ "MSHW0096" },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, surface_kbd_match);
+
+static struct platform_driver surface_kbd_driver = {
+	.probe = surface_kbd_probe,
+	.remove = surface_kbd_remove,
+	.driver = {
+		.name = "surface_keyboard",
+		.acpi_match_table = surface_kbd_match,
+		.pm = &surface_hid_pm_ops,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+module_platform_driver(surface_kbd_driver);
+
+MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
+MODULE_DESCRIPTION("HID legacy transport driver for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");
-- 
2.30.1

Re: [PATCH 0/2] HID: Add support for Surface Aggregator Module HID transport

[Hans de Goede]

Hi,

On 3/10/21 11:53 PM, Maximilian Luz wrote:
> This series adds support for the Surface System Aggregator Module (SSAM)
> HID transport subsystem.
> 
> The SSAM is an embedded controller, found on 5th- and later generation
> Microsoft Surface devices. On some of these devices (specifically
> Surface Laptops 1, 2, and 3, as well as Surface Book 3), built-in input
> devices are connected via the SSAM. These devices communicate (mostly)
> via normal HID reports, so adding support for them is (mostly) just a
> matter of implementing an HID transport driver.
> 
> SSAM actually has two different HID interfaces: One (legacy) interface
> used on Surface Laptops 1 and 2, and a newer interface for the rest. The
> newer interface allows for multiple HID devices to be addressed and is
> implemented in the first patch. The older interface only allows a single
> HID device to be connected and, furthermore, only allows a single output
> report, specifically one for the caps lock LED. This is implemented in
> the second patch.
> 
> See the commit messages of the respective patches for more details.
> 
> Regards,
> Max
> 
> Note: This patch depends on the
> 
>     platform/surface: Add Surface Aggregator device registry
> 
> series. More specifically patch
> 
>     platform/surface: Set up Surface Aggregator device registry
> 
> The full series has been merged into the for-next branch of the
> platform-drivers-x86 tree [1]. The commit in question can be found at
> [2].
> 
> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=for-next
> [2]: https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?h=for-next&id=fc622b3d36e6d91330fb21506b9ad1e3206a4dde

Jiri, I'll prepare an immutable branch with the necessary pdx86 pre-reqs for this
and I'll send you a pull-req for that IM branch, then you can merge these
through the HID tree after merging that pull-req.

Regards,

Hans



> 
> Maximilian Luz (2):
>   HID: Add support for Surface Aggregator Module HID transport
>   HID: surface-hid: Add support for legacy keyboard interface
> 
>  MAINTAINERS                                |   7 +
>  drivers/hid/Kconfig                        |   2 +
>  drivers/hid/Makefile                       |   2 +
>  drivers/hid/surface-hid/Kconfig            |  42 +++
>  drivers/hid/surface-hid/Makefile           |   7 +
>  drivers/hid/surface-hid/surface_hid.c      | 253 +++++++++++++++++
>  drivers/hid/surface-hid/surface_hid_core.c | 272 +++++++++++++++++++
>  drivers/hid/surface-hid/surface_hid_core.h |  77 ++++++
>  drivers/hid/surface-hid/surface_kbd.c      | 300 +++++++++++++++++++++
>  9 files changed, 962 insertions(+)
>  create mode 100644 drivers/hid/surface-hid/Kconfig
>  create mode 100644 drivers/hid/surface-hid/Makefile
>  create mode 100644 drivers/hid/surface-hid/surface_hid.c
>  create mode 100644 drivers/hid/surface-hid/surface_hid_core.c
>  create mode 100644 drivers/hid/surface-hid/surface_hid_core.h
>  create mode 100644 drivers/hid/surface-hid/surface_kbd.c
> 

Re: [PATCH 0/2] HID: Add support for Surface Aggregator Module HID transport

[Maximilian Luz]

On 3/10/21 11:53 PM, Maximilian Luz wrote:
> This series adds support for the Surface System Aggregator Module (SSAM)
> HID transport subsystem.
> 
> The SSAM is an embedded controller, found on 5th- and later generation
> Microsoft Surface devices. On some of these devices (specifically
> Surface Laptops 1, 2, and 3, as well as Surface Book 3), built-in input
> devices are connected via the SSAM. These devices communicate (mostly)
> via normal HID reports, so adding support for them is (mostly) just a
> matter of implementing an HID transport driver.
> 
> SSAM actually has two different HID interfaces: One (legacy) interface
> used on Surface Laptops 1 and 2, and a newer interface for the rest. The
> newer interface allows for multiple HID devices to be addressed and is
> implemented in the first patch. The older interface only allows a single
> HID device to be connected and, furthermore, only allows a single output
> report, specifically one for the caps lock LED. This is implemented in
> the second patch.
> 
> See the commit messages of the respective patches for more details.
> 
> Regards,
> Max
> 
> Note: This patch depends on the
> 
>      platform/surface: Add Surface Aggregator device registry
> 
> series. More specifically patch
> 
>      platform/surface: Set up Surface Aggregator device registry
> 
> The full series has been merged into the for-next branch of the
> platform-drivers-x86 tree [1]. The commit in question can be found at
> [2].
> 
> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=for-next
> [2]: https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?h=for-next&id=fc622b3d36e6d91330fb21506b9ad1e3206a4dde
> 
> Maximilian Luz (2):
>    HID: Add support for Surface Aggregator Module HID transport
>    HID: surface-hid: Add support for legacy keyboard interface
> 
>   MAINTAINERS                                |   7 +
>   drivers/hid/Kconfig                        |   2 +
>   drivers/hid/Makefile                       |   2 +
>   drivers/hid/surface-hid/Kconfig            |  42 +++
>   drivers/hid/surface-hid/Makefile           |   7 +
>   drivers/hid/surface-hid/surface_hid.c      | 253 +++++++++++++++++
>   drivers/hid/surface-hid/surface_hid_core.c | 272 +++++++++++++++++++
>   drivers/hid/surface-hid/surface_hid_core.h |  77 ++++++
>   drivers/hid/surface-hid/surface_kbd.c      | 300 +++++++++++++++++++++
>   9 files changed, 962 insertions(+)
>   create mode 100644 drivers/hid/surface-hid/Kconfig
>   create mode 100644 drivers/hid/surface-hid/Makefile
>   create mode 100644 drivers/hid/surface-hid/surface_hid.c
>   create mode 100644 drivers/hid/surface-hid/surface_hid_core.c
>   create mode 100644 drivers/hid/surface-hid/surface_hid_core.h
>   create mode 100644 drivers/hid/surface-hid/surface_kbd.c
> 

Hi, is there any status update on this?

Regards,
Max

Re: [PATCH 0/2] HID: Add support for Surface Aggregator Module HID transport

[Jiri Kosina]

On Wed, 10 Mar 2021, Maximilian Luz wrote:

> This series adds support for the Surface System Aggregator Module (SSAM)
> HID transport subsystem.
> 
> The SSAM is an embedded controller, found on 5th- and later generation
> Microsoft Surface devices. On some of these devices (specifically
> Surface Laptops 1, 2, and 3, as well as Surface Book 3), built-in input
> devices are connected via the SSAM. These devices communicate (mostly)
> via normal HID reports, so adding support for them is (mostly) just a
> matter of implementing an HID transport driver.
> 
> SSAM actually has two different HID interfaces: One (legacy) interface
> used on Surface Laptops 1 and 2, and a newer interface for the rest. The
> newer interface allows for multiple HID devices to be addressed and is
> implemented in the first patch. The older interface only allows a single
> HID device to be connected and, furthermore, only allows a single output
> report, specifically one for the caps lock LED. This is implemented in
> the second patch.
> 
> See the commit messages of the respective patches for more details.

Now queued in hid.git#for-5.13/surface-system-aggregator-intergration

Thanks,

-- 
Jiri Kosina
SUSE Labs